A Safe Drug for Morning Sickness

The next issue of The Medical Letter (August 5, 2013) includes an article on a new drug recently approved by the FDA for treatment of nausea and vomiting associated with pregnancy. It will be the only drug approved for such use in the US. Diclegis is new in name only. It is a fixed-dose combination of the H1-antihistamine doxylamine and the vitamin B6 analog pyridoxine. This combination was previously available in the US as Bendectin, but it was voluntarily withdrawn by its manufacturer in 1982. In the intervening 30 years, no drug was approved by the FDA for treatment of this common, often disabling condition.

Bendectin was widely used to treat morning sickness (which does not occur only in the morning) in the 1960’s and 1970’s. One estimate found that as many as 40% of all pregnant women in the US took Bendectin. Inevitably, some of these women delivered infants with birth defects, and just as inevitably, sued the manufacturer. Given the mindlessness of medical malpractice litigation in the US, the absence of any evidence of causality did nothing to stem the deluge of lawsuits that followed. The FDA defended Bendectin, saying there was no evidence that it was teratogenic, but the manufacturer chose to live to fight another day and withdrew the drug.

The withdrawal had one dramatic result: a 2-3 fold increase in hospitalizations for severe morning sickness. It did not lead to a decrease in the incidence of birth defects in general, or in the incidence of any particular congenital anomaly. The combination of doxylamine and pyridoxine continued to be available in Canada (as Diclectin), and multiple studies have found no evidence that it causes birth defects. It was the Canadian manufacturer (Duchesnay) that submitted a New Drug Application to the FDA for Diclegis. For the rest of the story, watch for our August 5th issue.

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  1. Why now? Zofran seems very effective and safe in this patient population and is available in generic at this time. Although Zofran does not have approval for this indication, it is, in fact, widely used for such.

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